Investigating the thermal force effect of the rail on dynamic analysis of railway track under dynamic load

Railways are always exposed to vertical, lateral, and axial loads that have different values ​​for various types of railways. Temperature changes due to rail contraction and expansion (thermal forces), acceleration and braking forces in wagons and locomotives, and many other factors cause high longitudinal forces in the railway tracks that not controlling these forces may reduce the stability of the tracks and eventually occur Buckling phenomenon. In this paper, first, the ballast railway system is modeled as a three-layer model using engineering software, and effects of not applying longitudinal force, applying longitudinal tensile and compressive longitudinal forces on parameters such as rail displacement, velocity and acceleration, sleeper velocity, and acceleration, ballast velocity and acceleration are investigated simultaneously with the application of a vertical moving load using the Wilson-Theta numerical method. Then, by performing sensitivity analysis for different values ​​of longitudinal force and different speeds of the train from 36 km / h to 360 km / h, changes in displacement, velocity, and acceleration of rails, sleepers, and ballasts are presented as time history diagrams. The results showed that increasing the values ​​of longitudinal force by increasing the speed of the train in the case of applying a vertical moving load has enhanced the value ​​of displacement, velocity, and acceleration both on the rails and in the sleeper and ballast.